I. General Information
     a. What is HD DVD?

What is HD DVD?
HD DVD, along with its chief competitor Blu-ray Disc (BD), is an optical storage technology designed with capacity and performance sufficient to meet the demands and expectations of high definition (HD) movie distribution and personal video recording.

The same physical size and appearance as CD and DVD, HD DVD operates using like principles whereby data is written to or read from a rotating disc by means of a focused laser light beam. However, whereas CD and DVD hold up to 700 MB and 8.5 GB respectively, HD DVD stores as much as 30 GB. The increased capacity (areal density) of HD DVD is achieved by employing smaller sized pits/marks and lands more tightly packed together to encode the data in the disc. These physical disc features can be read or written thanks to a smaller laser spot size created with a shorter blue wavelength laser focused through a larger numerical aperture objective lens. In part, higher performance comes by rotating the disc faster so that, whereas CD transfers 153,600 bytes of user data per second and DVD 1,385,000 bytes per second, HD DVD transfers 4,568,750 bytes per second (see chart).

As a movie platform, HD DVD supports both standard (SD) and high definition (HD) video, the latest multi-channel audio technologies as well as more sophisticated navigation, elaborate visual and interaction possibilities than those employed in DVD. To deter unauthorized copying of commercial material, HD DVD also incorporates more robust content management and protection mechanisms. Other personal and professional uses include computer data storage, archiving and software distribution as well as television broadcast and camcorder recording.

Misspellings: HD-DVD, HDDVD.

HD DVD/BD/DVD/CD Format Comparison

Characteristic	HD DVD	BD	DVD	CD
Capacity	12 cm SS: 15GB (ROM, R, RW SL), 30 GB (ROM, R, RW DL), 20 GB (RAM SL) 8 cm SS: 4.7GB (ROM SL), 9.4 GB (ROM DL) 12 cm DS: 30 GB (ROM, R, RW SL), 60 GB (ROM, R, RW DL), 40 GB (RAM SL) 8 cm DS: 9.4 GB (ROM SL), 18.8 GB (ROM DL)	12 cm: 25 GB (SL), 50 GB (DL) 8 cm: 7.79 (SL), 15.58 (DL)	12 cm SS: 4.7 GB (ROM, R, RW, RAM SL), 8.5 GB (ROM, R, RW DL) 8 cm SS: 1.46 GB (ROM, R, RW, RAM SL), 2.66 GB (ROM, R, RW DL) 12 cm DS: 9.4 GB (ROM, R, RW, RAM SL), 17 GB (ROM, R, RW DL) 8 cm DS: 2.92 GB (ROM, R, RW, RAM SL), 5.32 GB (ROM, R, RW DL)	12 cm: 700 MB 8 cm: 185 MB
Wavelength (nm)	405 (blue)	405 (blue)	650 (red)	780 (infrared)
Numerical aperture (NA)	0.65	0.85	0.6	0.5
Substrate/cover thickness (mm)	0.6 x 2	0.1 (SL), 0.075 (DL)	0.6 x 2	1.2
Laser spot size (µm)	0.55	0.58	1.32	2.11
Track pitch (µm)	0.4 (ROM, R, RW) 0.34 (RAM)	0.32	0.74 (ROM, R, RW) 0.615 (RAM)	1.6
Minimum pit/mark length (µm)	0.204 (ROM, R, RW) 0.173 - 0.187 (RAM)	0.149	0.4 (ROM, R, RW SL), 0.440 (ROM, R, RW DL) 0.420 - 0.437 (RAM)	0.8
Areal density (Gb/in2)	8.8	14.73	2.77	0.41
Channel bit rate (Mbps)	64.8	66	26.16 (ROM, R, RW) 58.36 (RAM)	4.3218
User data rate (Mbps)	36.55	35.965 (data), 53.948 (movie)	11.08 (data), 10.08 (video), 22.16 (RAM)	1.2288
User data per sector (bytes)	2,048	2,048	2,048	2,048
Reference velocity (m/s)	6.61 (ROM, R, RW) 5.64-6.03 (AM)	4.917 (data), 7.367 (movie)	3.49 (ROM, R, RW SL) 3.84 (ROM, R, RW DL) 8.16-8.49 (RAM)	1.3
Rotation (CCW)	CLV (ROM, R, RW), ZCLV (RAM)	CLV	CLV (ROM, R, RW), ZCLV (RAM)	CLV
Physical formats	ROM, C-ROM, R, R DL, RW, RW DL, RAM	ROM, R, RE	ROM, ±R, ±RW, RAM, ±R DL, ±RW DL	ROM, R, RW
Multiple physical format disc	Combo, Twin	Hybrid	DualDisc, DVDplus	SACD Hybrid
Application formats	ROM, HD DVD-V, HD DVD-VR	BD-ROM, BD-R/RE AV, BD-ROM AV (HDMV, BD-J)	DVD-ROM, DVD-V, DVD-A, DVD±VR, DVD-AR, DVD-SR, DVD-ENAV	CD-ROM, CD-DA, VCD, SVCD, CD-i, CD+G/M
Content protection	AACS	AACS, BD+, ROM Mark	CSS, CPPM, CPRM, VCPS	NA